The Little Sister and Star Island both explore Hollywood as a detrimental structure in society that suggests a lack of humanity. In The Little Sister, there are many musings regarding the shallow nature and self-absorption of the film industry. (Reference Marlowe's soliloquy on not feeling human.) This book details fame as a thing of disdain, and develops the theme by use of internal dialogue pondering the morality of Los Angeles/Hollywood culture. Star Island, while more lighthearted, ultimately centers around the same ideas. This time, the phony aspects of celebrity lifestyle are directly portrayed through the character of Cherry Pye, who is a talentless fraud despite her status. Both of these books champion integrity over greed. That point is much more blatantly made in Star Island, but resonates throughout both nonetheless. As for which one does it better, I suggest choosing which style of thematic explanation appeals to you the most as a reader, and go with that one. There isn't really a wrong answer there.